An XPS and SEM Study of Polyurethane Surfaces: Experimental Considerations

Abstract

Polyetherurethanes (PEU’s) are possibly the only class of polymeric material with mechanical properties which make them suitable for long-term application in an implanted total artificial heart. Evidence suggests that the surface composition of PEU’s influences, in a predictable manner, their interaction with blood (1, 2). Both attenuated total reflection infrared (ATR-IR) (3, 4) and X-ray photoelectron spectroscopy (XPS) (2,5,6,7,8) have shown that the surface compositions of these materials can differ considerably from the bulk, a surface excess of polyether segment being indicated. Since relationships between surface structure and blood compatibility have been established, an understanding of the factors which influence the nature of PEU surfaces might be used to fabricate PEU’s with improved blood compatibility. In this paper, a new method for calculating and presenting quantitative depth profiles of atomic composition derived from angular dependent XPS studies is considered. The method is based upon fitting angular XPS profiles, calculated employing a novel algorithm, to experimental data. Results have been obtained for a series of PEU compositions, with casting solvent and extraction as additional variables.